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What is RSI (Relative Strength Index)?

RSI — the Relative Strength Index — measures how fast and how far a stock has moved recently, on a scale of 0 to 100. It answers one question: has this stock been bought (or sold) too hard, too fast?

How to read the number

Example: A stock rallies 15% in eight sessions and RSI hits 78. Nothing is "wrong" with it — but buyers at this point are paying up after the move rather than before it. A patient buyer often gets a better price within days.

The classic beginner mistakes

Mistake 1: treating RSI 70 as an automatic sell. The strongest stocks stay overbought for long stretches. Selling a winner just because RSI crossed 70 is how people exit great trends early.

Mistake 2: buying just because RSI is below 30. In a confirmed downtrend, oversold is normal, not a bargain signal. RSI works best with the trend, not against it.

Mistake 3: using RSI alone. RSI describes speed, not direction or quality. A stock can have a healthy RSI while its trend is broken.

How RSI is actually calculated

RSI compares the average size of recent up-days against recent down-days (typically over 14 sessions). More and bigger up-days push it toward 100; the reverse pushes it toward 0. That's all it is — a speedometer for recent buying pressure.

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Educational only — not financial advice. This guide explains general concepts for learning purposes and is not a recommendation to buy or sell any security. Always do your own research and consult a licensed financial adviser before investing.

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